A judge has jailed Faisal Ellahi for 13 years for raping a young woman with Down syndrome.

Ellahi (34) who is originally from Haripur in Pakistan, had pleaded not guilty last year to rape, sexual assault and having sex with a mentally impaired person at his Dublin home on June 12, 2013. A jury at the Central Criminal Court convicted him of the rape and sexual assault charges.

Mr Justice Tony Hunt said he would not suspend any portion of the sentence as he hoped Ellahi would not be in the community on release. He said the crime, which had “carelessly demolished” the victim's independence, was at the lower end of the upper range in seriousness.

Judge Hunt commented that the “frightening, appalling, disgusting and depraved” offence committed by Ellahi had taken away years of work in helping the woman lead an independent life.

He said this was “all blown away for a couple of minutes of instant gratification”.

The judge noted that Ellahi had been out “prowling” the streets approaching another woman at the same time his victim was returning home.

He said some of the most difficult evidence in the case was the reaction of the woman's family members at her “dehumanised” state.

He complimented the victim's mother on her dignity and fortitude in meeting the case and wished the family well in future as they “restore” the woman to her independence.

He added that he hoped the Minister for Justice would take every step to remove Ellahi from the country when his sentence was completed.

Judge Hunt backdated the jail term to when he entered custody.

The trial heard that the victim told a specialist interviewer that Ellahi locked the door behind them and that she was afraid he was going to stab or kill her.

“I wanted to go home but he wouldn't let me,” she said. The woman said that at one point she panicked and started banging on the door screaming “help, mum, help.”

Ellahi gave evidence in his own defence in which he admitted propositioning many women as he walked the streets near his Dublin home. He said he would stop women and ask them to come home with him for “consensual fun”. He said he also used prostitutes.

The court heard evidence from 16 women who were approached by Ellahi in the area around the time of the rape. One women who lived across the road from him said he tried to force his way inside her home after she returned from a night out.

During his evidence Ellahi admitted “sexual contact” with the special needs victim but denied penetrative sex and claimed that he didn't know she had a mental impairment. He said she looked “normal” to him and that she enjoyed herself.

He said he never heard of Down syndrome until his arrest. He said in his native country people with mental impairments were kept at home or in hospitals and that they wore name badges to indicate they were disabled.

Ellahi moved to Ireland in 2005 where he found work as a security guard. He was unemployed at the time of the rape and spent his days walking the streets, he said.

A psychologist for the defence, Dr Rioghnach O'Leary said Ellahi came from an area of Pakistan where Sharia law was practised and where there were strict rules against physical contact between men and women.

She presented evidence that he was in the bottom three percent of the population in cognitive functioning and as a result “would have difficulty in adapting to social norms” in Ireland. However, because of time constraints, no “lie scale” testing was carried out which would show if the subject was attempting to skew the results of the intelligence tests.

The doctor also said that he showed an elevated sexual preoccupation and that he had a “singular focus on women as potential sexual partners.”

The trial heard that the woman had a mental age as low as seven in some areas and that she required supervision to do everything except wash and dress. An assessment found that she could not live independently or protect herself against serious exploitation.